So my engine started knocking and it is defintley a bottome end knock on 1993 Toyota T100

I was told by a mecahnic that my truck could last for 10 more days or another 20,000 miles it just depends. I recently just picked this truck up for 2500 dollars with a burnt out clutch and put a brand new clutch in it. I decided to sell my truck because i don't have the time or materials to put work into it. I put it up for 2,000 dollars and sold it for 1800. The guy is coming tomorrow to pick it up and i was wondering if i should of put it up for more. Everywhere i look it seems as if these trucks have a high value, so i was wondering how much value does my truck loose when this knocking starts? The truck is in great shape besides this.

engine knock due alot of the time to build up combustion chamber(ethanol blend in the fuel).
i have seen 1/2 tons from 2000 sell for less than $2000.00. most of time it is with owners that have not educated themselves about care and maintenence. some times thinking problem is worse than it actually is. problems with engine can get pretty costly. tough thing to take a loss on investment.
if the guy sees fit to pass after lookin at the truck, rec. ethanol treatment to 1 tank of premium. clean fuel system. ethanol blend in fuel causes build up in fuel system, combustion chambers, exhaust system and causes increased wear to spark plugs. this remedy is designed to clean all affected parts. it may help with engine knock.
rec. oil stabilizer treatment with oil change. recondition cylinders and seals(improve compression and hopefully quiet the knock).
rec. full tune up. replace old spark plugs with premium type plug(e3 spark plugs). examine ignition cables for signs of wear or damage(charring on boots). replace if needed. rec. upgrade to performance cables. accel's are good and more cost effective than OEM replacements.
rec. upgrade from conventional air filter to high flow design such as K&N.
examine drive links and replace whats needed(u joints, etc.).
examine shocks, replace if needed. rec. off road shocks.
get brakes inspected. replace if needed.
look for haines manual for instruction to tackle these issues yourself. these are things you can do to cut costs. for a few hundred extra dollars in parts and some elbow grease you may be able to increase the value of truck up to $3000.00 or $4000.00. these upgrades are selling points. find a young guy with testosterone coming out his ears to buy. of course it may just run so well you may want to keep it.
first things first, see about the sale. if no sale than bring to mech. for diagnostic run. see if it can pick up whats going on with engine.